Recovery of aluminum bromide catalyst



Patented May 16, 1944 nacovcmr or ALUMINUM naomn oa'ranrs'r Irving H. Welinsky, Media, Pa'., and Manuel H.

Gorin, Dallas, Tex, assiznors to Socony-Vacuum Oil Company, Incorporated, New York, N. Y., a corporation of New York Application September 24, 1942, Serial No. 459,542

' 12 Claims. (Cl. 23-96) This invention relates to the recovery of aluminum bromide from light tars which are formed in low temperature hydrocarbon conversion processes. These tars are presumably complex compounds formed by the interaction of aluminum bromide and the hydrocarbons, and settle out as an immiscible layer.

The use of aluminum bromide. to catalyze a low temperature hydrocarbon isomerization process has been disclosed in U. 8., Patent 2,288,477 to Charles W. Montgomery. The use of aluminum bromide to catalyze other low temperature hydrocarbon conversion reactions-such as alkylation reactions, reforming reactions, disproportionation reactions and condensation reactions has been disclosed in copending application Serial No. 448,886 filed June 29, 1942, by Will Swerdlofi and Manuel H. Gorin, one of us. Aluminum bromide is similar to aiuminumachloride in its catalytic activity for these low temperature hydrocarbon conversion processes and ofiers the advantage over aluminum chloride in that it is soluble in liquid hydrocarbons. Because of this solubility of aluminum bromide in liquid hydrocarbons more efilcient contacting between the catalyst and the hydrocarbon reactant is obtainable, than is possible with aluminum chloride. Also, since vigorous agitation is unnecessary by the use of aluminum bromide, it is economical to provide longer reaction time, thus conversion processes. A further object is to recover the aluminum bromide values substantially completely from such light tars.

'Still'another object is to recover the aluminum bromide in a form that is soluble in hydro-' carbons, and that is substantially free from hydrocarbons so that it may be reused directly in conversion processes apparently react with unmaking unnecessary the use of promoters such as halogen acids to increase the velocity of the hydrocarbon conversion reaction. For these and many other reasons aluminum bromide is very useful as a catalyst, and is superior to aluminum chloride in many respects.

Aluminum bromide is, however, considerably more expensive than aluminum chloride and in order to beable to utilize its advantages it should be efficiently recoverable for reuse in any process in which it is used as the catalytic agent. Thererecovery of aluminum bromide from the hydrocarbon immiscible tars containing it which are formed in these low temperature hydrocarbon saturated hydrocarbons, either present in the reaction mixture or formed in the presence of the catalyst through cracking reactions to form co'mplex organic-aluminum halide compounds. These compounds are substantially immiscible with the I hydrocarbons and therefore, are much less desirable as catalytic agents. In the case of aluminum chloride catalyststhey coat the surface of the solid catalyst and inhibit its catalytic activity. The aluminum chloride catalyst, therefore, should be regenerated while it is still in a condition in which it contains considerable amounts of uncombined aluminum chloride. plex organic-aluminum bromide compounds, on the other hand, settle out from the liquid hydrocarbon reaction mixture as an immiscible layer,

and are associated with a certain amount of additional saturated hydrocarbons soluble in the catalyst complex. The aluminum chloride organic catalyst complex is therefore usually a heavy tar or sludge, while the aluminum bromide catalyst complex resembles a light viscous tar, The aluminum bromide tar will usually contain from to percent by weight of aluminum bromide. While this organic-aluminum bromide complex apparently still has considerable catalytic activity, the advantage of solubility in the hydrocarbon is lost and hence the catalyst com- 45 plex should be withdrawn and the aluminum bromide recovered to render it suitable for reuse.

Many processes have been developed for the regeneration for aluminum chloride. These procv esses generally involve a simple heating of the sludge or heavy tar to distill oil? the aluminum chloride. This aluminum chloride distills over along. with the hydrocarbons that are volatile within the distillation temperature range. In U. S. Patent 1,520,080 by GeorgeI Prichard and Herbert Henderson, a typical process for the re- The comsludges is disclosed. The separation of alumi- .num chloride from the hydrocarbons presents no problem since aluminum chloride is insoluble in these hydrocarbons and condenses directly to a solid from which the liquid hydrocarbon condensate may be readily separated. The heating is continued until the recoverable, aluminum chloride has been distilled over, and the cokelike material, which still contains appreciable quantities of aluminum chloride and other aluminum compounds, is discarded.

Obviously such a process is not suitable for the more expensive aluminum bromide. thermore, such a distillation would produce but a limited separation of aluminum bromide and hydrocarbons. Aluminum bromide is considerably less volatile than aluminum chloride, and a large portion of the hydrocarbons would be distilled over therewith. Also, upon condensation of the'distilled vapors, the liberated aluminum.

Fur

bromide would go directly into solution in the hydrocarbons and would be recovered associated with a conglomerate mixture of hydrocarbons. To separate aluminum bromide from these hydrocarbons would involve further processing. Moreover, the major portion ofv the aluminum bromide would distillover in the form of the aluminum bromide-hydrocarbon complex, and would not be hydrocarbon soluble.

We have discovered that aluminum bromide may be recovered practically completely, and in a form substantially free from hydrocarbons by destructively distilling the light tar complex. This destructive distillation is preferably carried out by distilling the tar under conditions of total reflux of hydrocarbons boiling above about 00- C., until it has been completely reformed by the action of the heat in the presence of the catalyst to light fixed gases, aluminum bromide and high boiling hydrocarbons or coke. Th distillation is continued with total reflux until-this conversion is completed. The light, fixed gases formed are allowed to distill off. The temperature of the vapor distilling over will then level ofi at approximately the boiling point of aluminum bromide at the pressure in the system, indicating that all light hydrocarbon material has beendistilled' out from the catalyst mixture. The aluminum bromide may then be distilled over substantially-free from hydrocarbons. Apparently under the distillation temperature conditions, and in the presence of the catalytically active aluminum bromide hydrocarbon complex, the hydrocarbons ar reformed to a mixtur of normally gaseous hydrocarbons, predominantly methane and ethane along with some hydrogen and lesser amounts of other gases such as p pane, which are not condensable at atmospheric or moderately elevated pressures at temperatures above 100 C. in the condenser. These gases are removed from the system. Concurrently with the formation of these light fixed gases another portion of the hydrocarbons is reacted to form heavy, high boiling hydrocarbons which are not volatile at the boiling'point of aluminum bromide. By distilling the catalyst complex with total reflux of the tarry materials whose boiling point approaches that of aluminum bromide, the hydrocarbon complex is broken up and the hydrocarbons are completely converted to high and low boiling material. When this reaction has been completed the low boiling materials will already have been removed from the catalyst complex, and all that is then necessary is to distill over the aluminum bromide.

As is the. case with aluminum chloride, the continued heating of aluminum bromide to temperatures in the neighborhood of its boiling point in the presence of the hydrocarbons causes some of the aluminum bromide to chemically decompose. Bromine, apparently in the form of complex organic bromides or hydrogen bromide, is vaporized and will distill over along with the light fixed hydrocarbons and be lost. The addi tion of metallic aluminum in some form to the system so that it will be in contact with either the tar or the hot vapors coming oii from the tar before they pass through the condenser is preferable in order to avoid this loss. The vapors coming from the still DOt may be passed through a fractionating column that is packed with aluminum turnings. If desired, only a section of the column need be packed with aluminum.

Also the aluminum may be placed in the still.

pot itself, as aluminum turnings or aluminum powder. .Where an ordinary iron or steel still pot is used this placing of the aluminum in the still pot ofiels the additional advantag that the formation of iron bromides is substantially prevented. In the absence of metallic aluminum there is a tendency for the hot organic bromides or hydrogen bromide to react with the walls of the still pot'to form ferrous bromide. This compound is unstable in the presence of metallic aluminum and, under the conditions prevailing in the still pot, it will readily break down to iron and aluminum bromide. Where there is no aluminum in the still pot itself this material may condense to a solid on the cooler portions of the still pot or in the vapor line from the still pot to the fractionating column with the resulting loss of bromine. By the addition of some aluminum to the still pot where the hot tar is incontact with iron or steel surfaces either the iron bromide compounds are not formed or if they are formed, they rapidly are broken up. Hence, especially where an iron or steel still pot is used, the use of metallic aluminum both in the still pot and in the fractionating column may be desirable. Where the column or a section of the column is packed with aluminum, provision is preferabiy made for heating the aluminum. This heating of the aluminum in the column serves the double purpose of promoting the combination of the aluminum with volatile bromine compounds in the vapors, and of preventing the condensation of vapors in the aluminum packed column sections rather than in the condenser.

Our invention may be better understood by a study of the accompanying drawing and the specific examples illustrating the operation thereof. The description 'of the operation of the invention and the specific examples are to be considered as illustrative of our invention, and our invention is not to be considered as limited to the use of any particular apparatus.

The drawing is a diagrammatic illustration of an apparatus suitable for carrying out the invention.

Referring to the drawing, the light tar settling out as an immiscible layer from a low temperature hydrocarbon conversion reactor (not shown) is drawn oii and fed to the still pot I through line 2 provided with control valve 3. This still pot is heated by direct contact with the hot furnace gases in furnace 4 provided with gas burner 5. The vapors pass overhead from the still not the uncondensed gases.

-would be formed in considerable amounts. such cases aluminum should obviously be used to through line to packed column 1 provided with a suitable inert packing 8 and'thence through line 9 to the small column l0 packed with aluminum'turnings H and provided with a suitable electric resistance heating element 52. The vapors then pass through line H to condenser M I condense light fixed gases such as hydrogen and th light normally gaseous hydrocarbons such as methane, ethane and propane which are present in the overhead vapors; The condensate, together with the uncondensed fixed gases, passes through line l5 to receiver l6 wherein the liquid condensate accumulates and is separated from The uncondensed fixed gases pass out of the system through line H.

The aluminum bromide, and any intermediate boiling hydrocarbons and tar that are condensed are returned from the receiver to the top of the fractionating column I through .line l8 provided with valve l9. At the start of, the reaction there will be a considerable amount of intermediate boiling hydrocarbons and tar vaporized along with the aluminum bromide, and all of the aluminum bromide and other material condensed in the receiver It will be returned to the column I for further reflux. After a time the evolution of the fixed gases through line it will substantially cease and the temperature of overhead vapors in line l3 will level off at approximately that of the boiling point of aluminum bromide at the pres sure maintained in the system. When this occurs it is an indication that the intermediate boiling hydrocarbons have all. been cracked to fixed gases or heavy high boiling hydrocarbons and that aluminum bromide vapor in a substantially pure form is being driven off overhead.

Valve 2'0 is then opened to permit a portion of the aluminum bromide to flow through line ill to' storage tank 22 wherein purified aluminum bromide is recovered. for reuse. Some aluminum bromide is returned through line I8 to provide reflux for column 7 and this division of the flow of aluminum bromide at this stage of the process is controlledby suitable adjustment of the valves 99 and 20. Column I is provided-With the usual liquid return line 23' and a pump 24 so that the liquid reflux returning through the column may be returned to still pot l without interfering with the flow of vapor to the column through line t. While. the use of the bromine recovery column I0 is not essential to our invention, it has proved useful and results in the recovery of several percent of bromine which would otherwise volatilize as organic bromides along with. the

- fixed gases. With carefully controlled heating to avoid appreciable overheating of the light tar this formation of volatile bromine compounds may be kept at a very low figure making it unnecessary to pass the vapors through aluminum;

The necessity for the use of aluminum to recover the bromine which might otherwise be can ried over as light volatile organic bromides, hy drogen bromide 01' free bromine, would also depend very considerably upon the past history of the tar. For example, should the tar contain any appreciable amounts of oxygen or sulphur compounds, hydrogen bromide or alkyl bromides In react with the volatile brominev compounds to form aluminum bromide.

In the operation the light tar is heated in still i at a rate 'sufiicient to produce a steady evolution of vapors. The tar begins to froth and boil soon after heating begins and light hydrocarbons,

presumably in solution in the tar,- are given oif at temperatures below 100 C. After this evolution of gas, the temperaturelof the vapor rises fairly rapidly to about 200? C. (depending upon the rate of distillation and the pressure maintained in the system) and a mixture of fixed gases, tar and aluminum bromide vapors fill the column. At the higher temperatur then prevailing in the still and in the column, the aluminum bromide-hydrocarbon complex is decomposed and the hydrocarbons are cracked in the presence of the catalyst to fixed gases which pass out of the system, and to high boiling material, while the intermediate hydrocarbons and aluminum bromide vapors passing overhead are condensed and refluxed to the column. During this time the vapors in the column are reddish brown IN I in color indicating the volatilization of the aluminum bromide-hydrocarbon tar. After all 011; the fixed gases have been distilled off, the remaining hydrocarbons are considerably higher boiling than aluminum bromide which compound may then be distilled off in a substantially pure form. The temperature of overhead vapors will level ofi at that of the boiling point of aluminum bromide at the pressure in the system, and the vapors in the upper portion of the column passed overhead are colorless. The heat is applied to the still at a rate such that high boiling hydrocarbons do not distill over along with the aluminum bromide. This is done by controlling the distillation rate to prevent substantial temperature rise in the overhead vapors coming from the top of the column. It is necessary to finally heat the mate rial in the still pot to about 750 C. to obtain elficient recovery of the aluminum bromide. The

material remaining in the still pot resembles very heavy tar or coke-like residue and should be taken out before processing another batch of the light tar containing aluminum bromide, otherwise a, continued accumulation of this coke-like material on the walls of the still pot would efiectively insulate the contents of the still from the hot Example 1 The tarry residue settling out of a normal paraflin isomerization reaction, in which the reaction, carried out in the liquid phase, was catalyzed by aluminum bromide, was drawn ofi for recovery of the aluminum bromide'valuein the light tar. The tar was analyzed and showed a bromine content of 59.45%, or an aluminum bromide content of 65.59%. 2160 grams of this tar, containing 1427 grams of aluminum bromide were charged into a still pot mounted in a small gas fired furnace. The still pot was connected to an insulated column divided into two sections. The lower, larger section of the column was packed with glass beads, and theupper, smaller section was packed with aluminum turnings' The column was connected to a condenser through which a heat exchange fluid was circulated at a. to condense vatemperature and rate suflicient pors boiling above 100 C.. A line was provided for returning condensate to the, top of the lower section of the column. The flow lines, valves, etc., were insulated so that the temperature throughout the system would be maintained above the melting point of aluminum bromide. Very soon after heating began, the evolution of gases from a receiver used to collect the condensate, was observed. These gases were bubbled through an absorbing solution, so thatany bromine or bromine compounds which might not be condensed would not escape into the atmosphere, and also so that the amount of such bromine losses could be measured. This gas evolution from the receiver was considerable even before the temperature of the tar in the still not reached 100 C. The temperature of the tar was continuously raised, and when it passed 100? C., the evolution of vapor continued vigorously. The temperature of the still pot was continuously raised from an initial tar temperature of C. to an end temperature of 775 C. over a period of six hours. The temperature of the overhead vapors going to the condenser rose. rapidly to about 85 0., and then rose slowly upto the boiling point of aluminum bromide. During this time all of the condensate was recirculated to the top of thev lower section of the column. A heat ing jacket was provided around the upper section of the column and the aluminum turnings therein maintained at a temperature of approximately 500 C. When the temperature of the overhead vapors going to the condenser reached approximately the boiling point of aluminum bromide (259 0.), which occurred about five hours after the heat was first applied to the tar, a portion of the distillate was drawn off continuously as product.

The total amount of aluminum bromide collected was 1257 grams. The bromine content of the product was 88.3%. The bromine content of aluminumbromide is 89.98%, indicating that the purity of the product was 98.2%. On the. basis of theoretically pure aluminum bromide the recovery was 1232 grams out of 1427 grams in the original tar. An 86.5% recovery of aluminum bromide was indicated- Actually the recovery was better than this value given, since in working on small scale equipment, the amount of hold up in the condensers and column was material, and should not be charged against the process. The apparatus was flushed out and the aluminum bromide content of this hold up determined by analyzing for bromine. The indicated aluminum bromide in the hold up was 99 grams. Deducting the hold up from the amount charged, the actual aluminum bromide recovery was 1232 grams out of 1328 grams or 93.0%. About 5.8% of the original brominecontent of the tar remained combined in th coke-like residue. Less than 0.1% of the original bromine was;driven of! in the uncondensed vapors. Slightly over 1% of bromine was unaccounted for, presumably adsorbed on the packing material in the column. The results of this experiment would indicate that in large scale operation, after the packing had become saturated with aluminum bromide and/or other bromine compounds recovery of about 95% of the aluminum bromide content of the tar would be obtained.

Essentially our process consists in taking advantage of the catalytic activity of the aluminum bromide, in itself and in the form of its hydro carbon complex, to reform the hydrocarbons in the tar to higher boiling hydrocarbons and lower boiling hydrocarbons. A small amount of hydrogen is formed also. Any hydrogen and the normally gaseous hydrocarbons are removed from the reaction zone as they are formed. The'higher boiling hydrocarbons remain in contact with the catalytic material, and as the temperature is raised to recover' the aluminum bromide more completely,'u1timately the major portion of these high boiling hydrocarbons are broken up into'the end products, hydrogen and carbon. The reaction proceeds at an appreciable rate at temperatures above 200 C. although in order to carry it on at a practicable rate and to obtain a reasonably complete recovery, temperatures above the boiling point of aluminum bromide and pref;- erably above 300 C. should be used. As the hydrocarbons are reformed, more complex hydrocarbons of higher boiling point are formed, and presumably, some of these recombine with aluminum bromide to form more stable and complex aluminum bromid catalyst compounds. Apparently, higher temperatures are required: to liberate aluminum bromide from these more complex compounds. In any event we have found that more complete recovery is obtained when the tar is subjected to increasingly higher temperatures. The temperature of. the tar is therefore gradually raised to above 500 C., and preferably to 750 C. as the reaction proceeds. At about 700 C. practically all of the high boiling hydrocarbon complexes are broken down to carbon and the fixed gases, and substantially complete recovery of the aluminum bromide is obtained. Temperatures up to about 900 C. have been used, although heating above 750 C. produces but little improvement in the recovery obtained.

The light tar must be subjected to the elevated temperatures for a suflicient time to allow the desired reactions to proceed. Generally from two to six hours are required. The amount of reaction time depends, of course,-upon the mean temperaturedevel to which the tar is subjected. As this mean temperature level is raised, the rate of reaction is'accelerated. Using the preferred method of carrying out our reaction by permitting the volatile material to vaporize, and refluxing the aluminum bromide and intermediate boiling hydrocarbons and catalyst complex, the rate of .material may be heated up to temperatures of 500 to 600 C. very rapidly, since all of the products remain in the bomb, giving no chance for the premature escape of aluminum bromide contaminated with intermediate boiling hydrocarbons and catalyst complex. Since the initial temperatures to which the tar is subjected may be maintained at a much higher level, a considerably shorter reaction time is required.

In order to illustrate the results which may be obtained by destructively distilling the aluminum bromide tar in a bomb, the following example is given:

Excessively large rates ofvaporization Example 2 A steel bomb was fitted with a thermocouple so that the temperature of a liquid in the bottom portion thereof could be measured. The bomb was charged with 450 grams of the tarry residue settling out from the isomerization reaction described in Example 1, and grams of aluminum powder. This tar contained 295.0 grams of aluminum bromide. The bomb was'heated until the temperature as indicated by the thermocouple showed that the tar had reached a temperature of 525 C. Heat was supplied to the bomb at a rate suflicient to maintain the temperature constant at this level for an hour. During the heating the pressure rose as high as 7000 pounds per square inch. The heating was then discontinued and thegases from the bomb allowed to vent slowly through a steam jacketed condenser. The normally gaseous hydrocarbons passed through the condenser, while the aluminum bromide con densed. 224.2 grams of aluminum bromide were recovered in a receiver. The receiver was heated to maintain the aluminum bromide in the liquid state. The bromine content of the product was 87.7%, as against a bromine content for pure aluminum bromide of 89.98%, indicating a purity of 97.5%. mide the recovery was 218.8 grams. The recov-' cry of aluminumbromide was 74.1% .of that charged. The residue in the bomb was diflicult to thoroughly remove and quantitatively analyze for bromine. Approximately 50 grams of bromine, however, were present in this residue. Longer heating and/or exposure to higher temperature could be used to eifect the recovery of the major portion of the bromine value in this residue. The remaining 18.6 grams of bromine in the charge were probably lost as uncondensed aluminum bromide and as volatile bromine compounds. The formation of volatile bromine compounds could be largely elimina ed by heating to higher temperatures so that such compounds would; react more completely with aluminum carbide intermediate products, which have been observed in the decomposition of the tar. or by the addition of more metallic aluminum to the charge.

It is not possible, however, by subjecting the tar to practically instantaneous heating up to a temperature of 600 C. to 700 C. or higher, to accomplish the desired recovery. For example, where the tar is sprayed against a hot plate, a decomposition into coke, fixed gases, and alum num bromide is not obtained to any appreciable extent. The major portion of the material is vaporized as a mixture of the original catalyst-tar complex, aluminum bromide and inte mediate boiling hydrocarbons. This method does not result in the allowance of suiilcient time for the intermediate boiling hydrocarbons, either free or in combination with aluminum bromide, to reform to lower boiling, normally gaseous hydro- On the basis of pure aluminum brocarbons, and hydrogen and to highboilin complex hydrocarbons and coke. Of course, by com densing the vapors coming from the hot plate, and continuously recontacting them with the hot plate for a sufiicient period of time, the desired recovery could be obtained. This operation of the -hot plate as a reboiler for a fractionating column would be equivalent to the use of the conventional fractionator still pot.

The amount of reaction time "required is, of course, dependent upon the time required to bring the tar up to reaction temperature. To the extent that the rate of heating may be increased,

residue formed is largely suspended in the molten metal. The metal may be heated directly or may be withdrawn from the reactor and contacted with suitable heating and scrubbing media to re condition it for further use in treating fresh tar.

The procedure for reconditioning such contaminated molten metal bath is described more fully in the copending application of Armand J. Abrams and, one of us, Irving H. Welinsky, Serial No. 416,018, filed October 22, 1941, and in application Serial No. 373,075, filed January 1941, by

Armand J. Abrams.

Other modifications of our invention will be apparent to those skilled in the art, and the foregoing description is to be considered only as illustrative of the preferred procedures for carrying out our invention.

In the foregoing description of our invention we have shown that the catalyst containing tars should be heated for periods of upwards of one hour in order for a substantial portion of the complex to be broken up to yield free aluminum bromide in a recoverable form" Where some sacrifice in the amount of recovery may be permitted, or, under some special heating conditions, the destructive distillation might be performed to the desired extent in less than an hour. By the use of the term a prolonged period of time" in the appended claims, we refer to time periods which are generally upwards of one hour. We do not intend to be limited to this one hour as a definite time limit since heating periods of lesser duration may well be used. It is only necessary that the destrnctive distillation be carried on for a sufficient period of time to allow the cracking and reforming operations to proceed to an extent hydrocarbons, the remainder 'of the catalyst complex rendered suiiiciently high boiling to be separable from aluminum bromide thus liberated, and the hydrocarbons liberated from the decomposed catalyst complex reformed to light fixed gases and high boiling hydrocarbons or coke.

In the foregoing description of our invention and in the claims, we have referred to low temperature hydrocarbon conversion reactions. The reactions of the type, in which the tars are formed, from which aluminum bromide is recovered according to the process of this invention, are carried out at temperatures below'l50 to 200 0., although somewhat higher temperatures may be used in special cases.

Having described our invention and the manner in which it is carried out, what we claim is:

1. A process for the recovery of aluminum bromide which has been used to catalyze low temperature hydrocarbon conversion reactions seected from the group consisting of isomerization, alkylation, reforming, disproportionation, and condensation reactions in which the catalyst loses its efliciency by forming an immiscible, viscous, reaction product with a portion of the hydrocarbone, which comprises separating the immiscible,

catalyst-hydrocarbon complex from the hydro-' carbon reactants and product containing the soluble aluminum bromide, destructively distilling the catalyst complex under iractionating conditions with total reflux or vapors condensible at temperatures above 100 C., withdrawing non-condensed fixed gases formed from the aluminum bromide-hydrocarbon complex under the distillation conditions, continuing the distillation with total reflux of the condensible vapors until the vapors attain a relatively constant temperature at approximately the boiling. point of the catalyst at the pressure in the system, and then withdrawing condensed aluminum bromide vapor from the system.

2. A process for the recovery of aluminum bromide which has been used to catalyze low temperature hydrocarbon conversion reactions selected from the group consisting of isomerization, alkylation, reforming, disproportionation, and

condensation reactions in which the catalyst loses its efiiciency by forming an immiscible, viscous, reaction product with a portion of the hydrocar bons, which comprises separating the immiscible, catalyst-hydrocarbon complex from the hydrocarbon reactants and product containing the soluble aluminum bromide, destructively distilling the catalyst complex by subjecting it to a temperature between 300 C. and 900 C. in a heating zone for a long period-of time, whereby the hydrocarbon-catalyst complex is broken up and the hythen withdrawing condensed aluminum bromide,

3. A process for the recovery or aluminum bromide from light tarry complexes of the aluminum bromide with hydrocarbons formed in low temperature hydrocarbon conversion processes in which aluminum l romide is used as the catalytic agent, which comprises destructively distilling the catalyst containing tar by heating to a temperature between 300 C. and 900 0., passing the vapors evolved through a fractionating column to a condenser, condensing vapors condensible at temperatures higher than 100 6., separating oh the nbn-condensed vapors, returning all of the condensed vapors to the column as reflux, continuing the distillation with total reflux of the condensible vapors until the temperature of the vapors attains a relatively constant. level at approximately the boiling point of the catalyst at the pressure in the system, and then withdrawing and recovering condensed aluminum bromide from the system while continuing the distillation at a rate to maintain the temperature of the effiuent vapors at about the boiling point of the catalyst.

4. A process for the recovery of aluminum bromide from light tarry complexes of the aluminum bromide with hydrocarbons formed in low temperature hydrocarbon conversion processes in which aluminum bromide is used as the catalyst agent, which comprises destructively distilling the catalyst containing tar by heating to a temperavapors evolved over metallic aluminum and condensing vapor condensible at temperatures higher than 100 0., separating oil the non-condensed vapors, returning all of the condensed vapors to the column as reflux, continuing the the boiling point oi. the catalyst at the pressure through a fractionating column to a condenser, 7

in the system, and then withdrawing and recovering condensed aluminum bromide vapor from the system.

5. A process for the recovery of aluminumbromide from light tarry complexes of the aluminum bromide with hydrocarbons formed in low temture between 300 C. and'800 C., passing the vapors evolved through a fractionating column, then passing said vapors over metallic aluminum, and then passing the vapors to a condenser, condensing vapor condensible at temperatures higher than 0., separating ed the non-condensed vapors, returning all of the condensed vapors to the top of the fractionating column out of contact with the metallic aluminum as reflux, continuing the distillation with total reflux of the conde'nsible vapors until the temperature of the vapors attains a relatively constant level at approximately the boiling point or the catalyst at the pressure in the system, and then withdrawing and recovering condensed aluminum bromide vapor from the system.

6. A process for the recovery of aluminum bromide from light tarry complexes of the aluminurn bromide with hydrocarbons formed in low temperature hydrocarbon conversion processes in which aluminum bromide is used as the catalytic agent, which comprises destructively distilling the catalyst containing tar by heating to a temperature between 300 C. and 800 C., passing the vapors evolved through a fractionating column,

then passing said vapors over metallic aluminum, maintaining the temperature of the metallic aluminum-between about 450 C. and 550 C., then passing the vapors to a condenser, condensing vapor condensable at temperatures higher than 100 C., separating oil the non-condensed vapors, returning all of the condensed vapors to the top of the iractionating column out of contact with the metallic aluminum as reflux, continuing the distillation with total reflux of the condensible vapors until the temperature of the vapors attains a relatively constant level at approximately the boiling point of the catalyst at the pressure in the system, and then withdraw-. ing and recovering condensed aluminum bromide vapor from the system.

'I. A process for the recovery oi aluminum bromide from light tarry complexes of the aluminum bromide with hydrocarbons formed in low temperature hydrocarbon conversion processes in which aluminum bromide is used as the catalytic agent, which comprises destructively distilling the catalyst containing tar by heating to about 300 C., passing the vapors evolved through a fractionating column to a condenser, condensing the vapors condensible at temperatures higher than 100 0., separating oil the non-condensed vapors, returning all of the condensed vapors to the column as reflux,. progressively raising the temperature of the tar to from 700 C. to 800 C. at a rate so as to maintain a substantially constant evolution of vapor, continuing the distillation with total reflux of the condensible vapors until the vapors attain a relatively constant tem- -perature at approximately the boiling point of the catalyst at the pressure in the system, and then withdrawing and recovering condensed aluminum bromide vapor from the'system.

8. A process for the recovery of aluminum bromide from light tarry complexes of the aluminum bromide with hydrocarbons iormed in low temperature hydrocarbon t conversion processes in which aluminum bromide is used as the catalytic agent, which comprises destructively distilling the catalyst containing tar by heating to a temperature between 300 C. and 800 C. in a heating zone for a prolonged period of time until the hydrocarbon-aluminum bromide complex is broken up and the hydrocarbons liberated are reformed to normally gaseous materials and a cokelike carbonaceous residue, maintaining conditions under which substantial amounts or the aluminum bromide remain in contact with the cataarating off the non-condensed vapors, returning thecondensate to the column as reflux, continuing the distillation with total reflux of the condensible'vapors until the vapors" attain a relatively constant temperature at approximately the boiling point of the catalyst at the pressure in the system, and then withdrawing and recovering condensed aluminum bromide from the system.

mide which has been used to catalyze low temperature hydrocarbon conversion reactions selected from the group consisting of isomerization, alkylation, reforming, disproportionation, and condensation reactions in which the catalyst loses, its emciency by forming an immiscible, viscous, reaction product with a portion of the hylyst-hydrocarbon 'complexin said heating zone for said prolonged period of time, permitting the escape of the normally gaseous material from the heating zone, and condensing and recovering the aluminum bromide vaporized oil from said heating zone after said prolonged period of time.

9. A process for the recovery of aluminum bromide from light tarry complexes of the aluminum bromide with hydrocarbons formed in low temperature hydrocarbon conversion processes in winch aluminum bromide is used as the catalytic agent, which comprises adding a small amount of metallic aluminum to the tar, destructively distilling the catalyst-containing tar by heating in admixture with the metallic aluminum to a temperature between 300 C. and 900 C. for a pro-- longed period -01 time, maintaining conditions under which substantial amounts of the aluminum bromide remain in contact with the catalyst-hydrocarbon complex tor said prolonged period of time, whereby said complex is broken up and the hydrocarbons liberated .are reiormed to normally gaseous materials and a coke-like car- .bonaceous residue, separating the normally gaseous materials, distilling the aluminum bromide from the coke-like residue and recovering said aluminum bromide.

10. A process for the recovery oi aluminum bromide from light tarry complexes of the aluminum bromide with hydrocarbons formed in low temperature hydrocarbon conversion processes in which aluminum bromide is used as the catalytic agent, which comprises adding a small amount of metallic'aluminum to the tar, destructively distilliiig the catalyst containing tar by heating it in admixture with the metallic aluminum to a temperature between 300 C. and 900 C. tor a prolonged period of time in a heating zone, passing the vapors evolved through a fractionating column to a condenser, condensing vapors condensible at temperatures higher than 100 C. sepdrocarbons, which comprises separating the immiscible, catalyst-hydrocarbon complex from the hydrocarbon reactants and product containing the soluble aluminum bromide, destructively distilling the catalyst complex by heating catalysthydrocarbon complex to a temperature between 300 C. and 900 C. for a prolonged period of time, maintaining conditions under which substantial amountsof the alumium bromide catalyst material remain in contact with the hydro-' carbon complex and hydrocarbons for said prolonged period or time, whereby said complex is broken up and the hydrocarbons liberated are reformed to fixed gases and a coke-like carbonaceous residue, separating the fixed gases and distilling and recovering the aluminum bromide vaporized oil from the coke-like residue after said prolonged period of time.

12. A process for the recovery of aluminum bromide which has been used to catalyze low temperature hydrocarbon conversion reactions selected from the group consisting of isomerization, alkylation, reforming, disproportionation, and condensation reactions in which the catalyst loses its efliciency by forming an immiscible, viscous, reaction product with a portion of the hydrocarbons, which comprises separating the immiscible, catalyst-hydrocarboncomplex from the hydrocarbon reactants and product, destructive- 1y distilling the catalyst complex by heating catalyst-hydrocarbon complex to a temperature about 500 C. for a prolonged period oi time,

maintaining conditions under which substantial 11. A process for the recovery of aluminum bro- 

